Semiconductor device and method of manufacturing the same

ABSTRACT

The present invention relates to a semiconductor device in which an interlayer insulating film having a low dielectric constant is formed by covering wiring primarily made of a copper film, and to a method of manufacturing the same. As for the constitution of the method of manufacturing a semiconductor device in which an insulating film  34  having a low dielectric constant is formed on a substrate  21  by allowing a film-forming gas to be converted into a plasma state and to react, the method comprises a step of forming a low-pressure insulating film  34   a  that constitutes the insulating film  34  on the substrate  21  by allowing said film-forming gas at first gas pressure to be converted into a plasma state and to react, and a step of forming a high-pressure insulating film  34   b  that constitutes the insulating film  34  on the low-pressure insulating film  34   a  by allowing the film-forming gas at second gas pressure being higher than the first gas pressure to be converted into a plasma state and to react.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor device in which an interlayer insulating film having a low dielectric constant is formed by covering wiring primarily made of a copper film, and to a method of manufacturing the same.

[0003] 2. Description of the Prior Art

[0004] In recent years, speeding-up of data transfer speed has been required along with progress of higher integration and higher density in semiconductor integrated circuit devices. For this reason, an insulating film that has a low dielectric constant for small RC delay (hereinafter referred to as a low dielectric insulating film) is used.

[0005] In order to form such low dielectric insulating film, a plasma enhanced CVD method that uses trimethylsilane (SiH(CH₃)₃) and N₂O is known as one method. For example, it is described in “M. J. Loboda, J. A. Seifferly, R. F. Schneider, and C. M. Grove: Electrochem. Soc. Fall Meeting Abstracts, p.344, (1998)” and the like. As for another plasma enhanced CVD method that uses tetramethylsilane (Si(CH₃)₄) and N₂O, description is made in “J. Shi, M. A- Plano, T. Mountsier, and S. Nag, SEMICON Korea Technical Symposium 2000, p.279 (2000)” and the like.

[0006] In addition, also known is a plasma enhanced CVD method that uses phenylsilane and the like. For example, it is described in “Kazuhiko Endo, Keisuke Shinoda, Toru Tatsumi: The Japan Society of Applied Physics The 46th Spring Meeting Digests (1999), p897,” “Nobuo Matsushita, Yoshinori Morisada, Yuichi Naito, Aya Matsunoshita: The Japan Society of Applied Physics The 60th Fall Meeting Digests (1999), 1p-ZN-9 (1999),” “Yasutaka Uchida, Takeo Matsuzawa, Satoshi Kanno, Masakiyo Matsumura: The Japan Society of Applied Physics The 4th Spring Meeting Digests, p.897 (1999)” and the like.

[0007] However, the low dielectric insulating film formed by the above-mentioned methods is relatively weak in adhesion strength with wiring primarily made of a copper film and is low in film hardness. Improvements are therefore expected.

SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide a method of manufacturing a semiconductor device capable of forming an insulating film that has a low dielectric constant, the insulating film also having a good adhesion property with wiring primarily made of a copper film and appropriate film hardness, and a semiconductor device produced by the method.

[0009] In this invention, film forming is performed by adjusting pressure of a film-forming gas. Specifically, film forming is performed under low gas pressure at an initial stage of film forming, then under high gas pressure for the remainder.

[0010] For example, the invention has a step of forming an insulating film (hereinafter, referred to as a low-pressure insulating film) on a substrate by converting a film-forming gas into a plasma state under the gas pressure below 1 Torr for reaction, and a step of forming an insulating film (hereinafter, referred to as a high-pressure insulating film) on the low-pressure insulating film by converting a film-forming gas formed into a plasma state under the gas pressure of 1 Torr or higher for reaction.

[0011] According to an experiment carried out by the inventor of the present invention, as shown in FIG. 2, exfoliation intensity between the substrate and the insulating film is inversely proportional to the gas pressure of the film-forming gas. Particularly, the exfoliation intensity rises extremely high under gas pressure below 1 Torr. On the contrary, as shown in FIG. 6, the dielectric constant of the formed film is high in the film formed under low gas pressure, and low in the film formed under high gas pressure.

[0012] Accordingly, film forming is performed by reaction with the film-forming gas of low gas pressure converted into a plasma state at the initial stage of film forming, thereafter, film forming is performed by converting the film-forming gas of high gas pressure into plasma for reaction, whereby an insulating film with high adhesion and of a low dielectric constant as a whole can be formed. In the experiment, film forming is performed on a silicon substrate, however, the same result may be obtained in a case when film forming is performed on a copper substrate.

[0013] In particular, when insulating films including a barrier insulating film are formed on wiring primarily made of a copper film, the barrier insulating film is formed by the method of manufacturing a semiconductor device of the present invention. Specifically, initial film forming is performed so as to form a low-pressure insulating film, and the remainder is formed as a high-pressure insulating film. As for a frequency of electric power for forming plasma, a low frequency is set for both the low-pressure insulating film and the high-pressure insulating film.

[0014] Basically, film forming with electric power of a low frequency imparts strong adhesion force, however, the adhesion strength even increases more when film forming is performed by use of a film-forming gas of low pressure at the initial stage of the film forming.

[0015] In addition, using a nitrogen-containing gas such as ammonia (NH₃) or nitrogen (N₂) as a film-forming gas of a barrier insulating film improves a barrier property. Alternatively, by using nitrogen (N₂), an inert gas such as helium (He) or argon (Ar) or the like, the film-forming gas can be diluted without losing the adhesion force of the formed film.

[0016] The foregoing invention is applied to a method of forming a barrier insulating film as a base for the main insulating film and a main insulating film having a low dielectric constant. However, within an object of just forming the main insulating film having a low dielectric constant, the gas pressure does not have to be changed during the film forming. In this case, by use of a film-forming gas containing: an alkyl compound having a siloxane bond; any one of acetylene (C₂H₂), methylcyclohexane (CH₃C₆H₁₁) and cyclohexane (C₆H₁₂); and an oxygen-containing gas, or a film-forming gas including; an alkyl compound having a siloxane bond; benzene (C₆H₆); an oxygen-containing gas; and an inert gas, a desired main insulating film can be formed while maintaining an equal gas pressure.

[0017] As for the film-forming gas, one containing methylsilane (SiH_(n)(CH₃)_(4-n): n=0, 1, 2, 3) instead of the alkyl compound having a siloxane bond may be used.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a side view showing a constitution of a plasma film-forming apparatus used for a method of manufacturing a semiconductor device according to an embodiment of the present invention.

[0019]FIG. 2 is a graph showing a relation of exfoliation intensity to gas pressure of a film-forming gas for a low dielectric insulating film according to a first embodiment of the present invention.

[0020]FIG. 3 is a graph showing a relation of exfoliation intensity to low-frequency electric power for substrate bias in the event that the film-forming gas for the low dielectric insulating film according to the first embodiment of the present invention is converted into plasma.

[0021]FIG. 4 is a graph showing relations of film hardness and Young's modulus to the gas pressure of the film-forming gas for the low dielectric insulating film according to the first embodiment of the present invention.

[0022]FIG. 5 is a graph showing relations of film hardness and Young's modulus to the low-frequency electric power for substrate bias in the event that the film-forming gas for the low dielectric insulating film according to the first embodiment of the present invention is converted into plasma.

[0023]FIG. 6 is a graph showing relations, each of a relative dielectric constant to the low-frequency electric power for substrate bias in the event that the film-forming gas for the low dielectric insulating film according to the first embodiment of the present invention is converted into plasma.

[0024]FIG. 7 is a view showing procedures of film forming according to the first embodiment of the present invention.

[0025]FIG. 8A and FIG. 8B are cross-sectional views showing a semiconductor device and a method of manufacturing the same according to a second embodiment of the present invention.

[0026]FIG. 9A and FIG. 9B are cross-sectional views showing a semiconductor device and a method of manufacturing the same according to a third and a fourth embodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Embodiments of the present invention will be explained with reference to the accompanying drawings hereinafter.

First Embodiment

[0028]FIG. 1 is a side view showing a configuration of the parallel-plate type plasma enhanced CVD film forming apparatus 101 employed in a film forming method according to an embodiment of the present invention.

[0029] This plasma enhanced CVD film forming apparatus 101 comprises a film forming portion 101A that is the place at which a silicon-containing insulating film is formed by the plasma gas on a substrate 21 subject to a film formation (hereinbelow, referred to as a substrate), and a film forming gas supplying portion 101B having a plurality of gas supply sources constituting the film forming gas.

[0030] As shown in FIG. 1, the film forming portion 101A has a chamber 1 whose pressure can be reduced, and the chamber 1 is connected to an exhausting device 6 via an exhaust pipe 4. A switching valve 5 for controlling the open and the close between the chamber 1 and the exhausting device 6 is provided in the middle of the exhaust pipe 4. A pressure measuring means such as a vacuum gauge (not shown) for monitoring the pressure in the chamber 1 is provided to the chamber 1.

[0031] A pair of opposing upper electrode (second electrode) 2 and lower electrode (first electrode) 3 are provided to the chamber 1. A high frequency power supply (RF power supply) 7 for supplying a high frequency power having a frequency of 13.56 MHz is connected to the upper electrode 2, while a low frequency electric power supply 8 for supplying a low frequency electric power having a frequency of 380 kHz is connected to the lower electrode 3. The film forming gas is plasmanized by supplying the power to the upper electrode 2 and the lower electrode 3 from these power supplies 7, 8. The upper electrode 2, the lower electrode 3, and the power supplies 7, 8 constitute the plasma generating means for plasmanizing the film forming gas.

[0032] The upper electrode 2 is also used as a film forming gas distributor. A plurality of through holes are formed in the upper electrode 2, and opening portions of the through holes in the surface opposing to the lower electrode 3 serve as discharge ports (inlet ports) of the film forming gas. The discharge ports of the film forming gas, etc. are connected to the film forming gas supplying portion 101B via a pipe 9 a. Also, a heater (not shown) may be provided to the upper electrode 2, as the case may be. This is because, if the upper electrode 2 is heated at the temperature of almost 100° C. during the film formation, particles made of reaction products of the film forming gas, etc. can be prevented from sticking onto the upper electrode 2.

[0033] The lower electrode 3 is also used as a loading table for the substrate 21. A heater 12 for heating the substrate 21 on the loading table is provided to the lower electrode 3.

[0034] In the film forming gas supplying portion 101B, a supply source for the alkyl compound having siloxane bond; a supply source for methyl silane (SiH_(n)(CH₃)_(4-n):n=0, 1, 2, 3); a supply source for any one of acetylene(C₂H₂), cyclohexane (C₆H₁₂) and methylcyclohexane (CH₃C₆H₁₁); a supply source for benzene (C₆H₆); a supply source for any one methylalcohole (CH₃OH) and ethylalcohole (C₂H₅OH); a supply source for oxygen-containing gas; a supply source for ammonia (NH₃); a supply source for inert gas; and a supply source for the nitrogen (N₂) are provided.

[0035] These gases are supplied appropriately to the chamber 1 of the film forming portion 101A via branch pipes 9 b to 9 j and a pipe 9 a to which all branch pipes 9 b to 9 j are connected. Flow rate controlling means 11 a to 11 i and switching means 10 b to 10 n, 10 p to 10 t for controlling the open and the close of the branch pipes 9 b to 9 j are provided in the middle of the branch pipes 9 b to 9 f. A switching means 10 a for controlling the open and the close of the pipe 9 a is provided in the middle of the pipe 9 a.

[0036] Also, in order to purge the residual gas in the branch pipes 9 b to 9 e, 9 g, 9 h by flowing the N₂ gas, switching means 10 u to 10 z for controlling the open and the close between the branch pipe 9 j, that is connected to the N₂ gas supply source, and remaining branch pipes 9 b to 9 e, 9 g, 9 h are provided. The N₂ gas purges the residual gas in the pipe 9 a and the chamber 1 in addition to the branch pipes 9 b to 9 e, 9 g, 9 h. In addition, the N₂ gas also is employed as a diluting gas as the case may be.

[0037] According to the film forming equipment 101 described above, the supply source for supplying the alkyl compound having siloxane bond, the supply source for supplying the hydrocarbon, the supply source for supplying the oxygen-containing gas and the supply source for supplying the inert gas are provided, and also the plasma generating means 2, 3, 7, 8 for plasmanizing the film forming gas are provided. In addition, the exhausting device 6 and flow rate controlling means 11 a to 11 i are provided.

[0038] Therefore, as shown in embodiments described in the following, it is possible to form the insulating film that has the low dielectric constant, and the strong adhesion force to a wiring primarily made of a copper film.

[0039] A means for generating a plasma by the upper and lower electrodes 2, 3 of parallel-plate type is employed as a plasma generating means, and the power supplies 7, 8 for supplying the powers having two high and low frequencies are connected to the upper and lower electrodes 2, 3 respectively. Therefore, the plasma can be generated by applying the powers having these two high and low frequencies to the electrodes 2, 3 respectively. Thus, the insulating film formed in this manner is dense, and the insulating film has a low dielectric constant as CH₃ is contained in the insulating film.

[0040] The followings are preferable combinations with respect to application of power to the upper and lower electrodes 2, 3.

[0041] First, in a process of forming a low-pressure insulating film, a low frequency electric power of 100 kHz or more and less than 1 MHz is applied to the lower electrode 3, or the low frequency electric power is applied to the lower electrode 3 and a high frequency electric power of 1 MHz or more is applied to the upper electrode 2. And in a process of forming a high-pressure insulating film, a high frequency electric power is applied to the upper electrode 2.

[0042] Second, in a process of forming a high-pressure insulating film, the low frequency electric power is applied to the lower electrode 3 in addition to applying the high frequency electric power to the upper electrode 2.

[0043] Third, in particular, in case of forming the lower pressure insulating film by employing the film forming method for forming a barrier insulating film of an insulating film including the barrier insulating film, the low frequency electric power of 100 kHz or more and less than 1 MHz is applied to the lower electrode 3, and in a process of forming a high-pressure insulating film, the low frequency electric power is applied to the lower electrode 3. In this case, the high frequency power may be applied to the upper electrode 2.

[0044] As for the alkyl compound having the siloxane bond, the methyl silane, the hydrocarbon, the oxygen containing gas and the diluting gas as the film forming gas to which the present invention is applied, followings may be employed as the typical examples.

[0045] (i)alkyl compound having siloxane bond hexamethyldisiloxane(HMDSO: (CH₃)₃Si—O—Si(CH₃)₃) Octamethylcyclotetrasiloxane(OMCTS: ((CH₃)₂)₄Si₄O₄

[0046] tetramethylcyclotetrasiloxane(TMCTS: (CH₃H)₄Si₄O₄

[0047] (ii)methylsilane (SiHn(CH3)4-n:n=0, 1, 2, 3)

[0048] monomethylsilane (SiH₃(CH₃))

[0049] dimetylsilane (SiH₂(CH₃)₂)

[0050] trimethylsilane (SiH(CH₃)₃)

[0051] tetramethylsilane (Si(CH₃)₄)

[0052] (iii)hydrocarbon (C_(x)H_(y))

[0053] acetylene (C₂H₂)

[0054] methylcyclohexan (CH₃C₆H₁₁)

[0055] cyclohexan (C₆H₁₂)

[0056] benzene (C₆H₆)

[0057] (iv)oxygen containing gas

[0058] N₂O

[0059] water (H₂O)

[0060] carbon dioxide (CO₂)

[0061] (v)diluting gas

[0062] helium (He)

[0063] argon (Ar)

[0064] nitrogen (N₂)

[0065] The examinations performed by the inventor of the present application are described hereinafter.

[0066] A silicon insulating film was formed on a Si substrate using plasma enhanced CVD method (PE-CVD method) under the following film forming condition. The HMDSO was employed as the alkyl compound having siloxane bond, the N₂O as the oxygen containing gas, and the He as the diluting gas. In addition, one minute and thirty seconds are taken as a period (a stabilizing period) for substitution of gases in the chamber from the gas introduction to the chamber to a start of the film formation, and the upper electrode 2 is heated at 100 ° C. to prevent reaction products from sticking to the upper electrode 2. Film-forming gas HMDSO flow rate:  50 sccm N₂O flow rate: 200 sccm He flow rate: 400 sccm gas pressure (parameter): 0.75 to 1.75 Torr

Conditions for Plasma Excitation

[0067] Lower electrode (first electrode)

[0068] low-frequency electric power (frequency 380 kHz) (parameter): 0 to 100 W

[0069] Upper electrode (second electrode)

[0070] high-frequency electric power (frequency 13.56 MHz) (parameter): 250 W

[0071] Condition for substrate heating: 375° C.

[0072] (a) Relation Between Gas Pressure of Film-forming Gas and Exfoliation Intensity

[0073]FIG. 2 is a view showing a relation between gas pressure of a film-forming gas and exfoliation intensity of a film formed on a silicon substrate. The axis of ordinates thereof shows the exfoliation intensity (gw) of a formed film scaled by linear graduations, and the axis of abscissas thereof shows the gas pressure (Torr) of a film-forming gas scaled by linear graduations.

[0074] Insulating films for examination were formed on silicon substrates in accordance with the parameters of the above-described conditions for film forming except that application of the low-frequency electric power to the lower electrode 3 was not carried out, and under two conditions of the gas pressure of the film-forming gas by 0.9 and 1.5 Torr, respectively. The exfoliation intensity was measured by use of a measurement instrument made by Shimadzu Corporation (Shimadzu Scanning Scratch Tester SST101.)

[0075] According to FIG. 2, the exfoliation intensity, which was in the range from 5 to 6 gw in the case of the gas pressure of 1.5 Torr, was significantly improved in the case of the gas pressure of 0.9 Torr by nearly three times, which was in the range from 15 to 16 gw.

[0076] It should be noted that, although a silicon substrate was used as a substrate subject to film forming and the exfoliation intensity was examined with respect to the silicon substrate in the above examination, it is conceivable that the exfoliation intensity with respect to a copper substrate would show a similar tendency.

[0077] (b) Relation Between Low-frequency Electric Power for Bias to Substrate Subject to Film Forming and Exfoliation Intensity

[0078]FIG. 3 is a view showing a relation between low-frequency electric power of the plasma-excited condition applied to the lower electrode 3 and exfoliation intensity of a film formed on a silicon substrate. The axis of ordinates thereof shows the exfoliation intensity (gw) of a formed film scaled by linear graduations, and the axis of abscissas thereof shows the low-frequency electric power (W) scaled by linear graduations.

[0079] Insulating films for examination were formed on silicon substrates in accordance with the above-described conditions for film forming while setting the gas pressure of the film-forming gas to 1.5 Torr, and under six conditions of the low-frequency electric power of 0, 10, 30, 50, 75 and 100 W, respectively.

[0080] The same measurement instrument as in the case (a) was used.

[0081] According to FIG. 3, as shown in the range of the low frequency electric power up to 30 W, the exfoliation intensity decreased as the electric power increased, such as from some 6 gw at 0 W to some 3.3 gw at 30 W. When the low-frequency electric power exceeded 30 W, the exfoliation intensity did not decrease significantly, and was settled around 3 gw.

[0082] (c) Relation Between Gas Pressure and Film Hardness

[0083]FIG. 4 is a view showing relations between gas pressure of a film-forming gas and film hardness as well as Young's modulus of a film formed on a silicon substrate. The left axis of ordinates thereof shows the film hardness of a formed film scaled by linear graduations, while the right axis of ordinates shows Young's modulus (GP) of the formed film scaled by linear graduations. The axis of abscissas shows tile gas pressure (Torr) of a film-forming gas scaled by linear graduations.

[0084] Insulating films for examination were formed on silicon substrates in accordance with the above-described conditions for film forming except that application of the low-frequency electric power to the lower electrode 3 was not carried out, and under six conditions of the gas pressure of the film-forming gas of 0.7, 0.9, 1.1, 1.3, 1.5 and 1.7 Torr, respectively.

[0085] The film hardness and Young's modulus were measured by use of a measurement instrument made by Shimadzu Corporation (Shimadzu Dynamic Ultra Micro Hardness Tester DUH-W201S).

[0086] According to FIG. 4, in a range of the gas pressure from 0.7 Torr to 1.3 Torr, the film hardness decreases as the gas pressure increases. The film hardness was about 230 when the gas pressure was 0.7 Torr, and around 70 to 80 when the gas pressure was 1.3 Torr. When the gas pressure exceeded 1.3 Torr, the film hardness did not significantly change any more, and was settled around 50.

[0087] Young's modulus also showed a tendency substantially similar to that of the film hardness. Young's modulus was about 40 GP when the gas pressure was 0.7 Torr, and it was about 10 GP when the gas pressure was 1.3 Torr. When the gas pressure exceeded 1.3 Torr, Young's modulus was settled around 10 GP.

[0088] (d) Relation Between Low-frequency Electric Power for Bias to Substrate Subject to Film Forming and Film Hardness

[0089]FIG. 5 is a view showing relations between low-frequency electric power applied to the lower electrode 3 for forming direct current bias voltage to a substrate subject to film forming, and film hardness as well as Young's modulus of a film formed on a silicon substrate. The left axis of ordinates thereof shows the film hardness of a formed film scaled by linear graduations, while the right axis of ordinates shows Young's modulus (GP) of the formed film scaled by linear graduations. The axis of abscissas shows the low-frequency electric power (W) scaled by linear graduations.

[0090] Insulating films for examination were formed on silicon substrates in accordance with the above-described conditions for film forming while setting the gas pressure of the film-forming gas to 1.5 Torr, and under six conditions of the low-frequency electric power of 0, 10, 30, 50, 75 and 100 W, respectively. The same measurement instrument as in the case (c) was used.

[0091] According to FIG. 5, in a range of the low-frequency electric power from 0 to 75 W, the film hardness increases along with an increase of the electric power. When the low-frequency electric power exceeds 75 W, the increase of the film hardness becomes gentle. The film hardness was about 50 when the low-frequency electric power was not applied, about 290 at 75 W, and about 300 at 100 W.

[0092] Young's modulus also showed a tendency similar to that of the film hardness. Young's modulus was about 8 GP when the low-frequency electric power was not applied, about 47 GP at 75 W, and about 50 at 100 W.

[0093] (e) Relation Between Low-frequency Electric Power of Bias of Substrate Subject to Film Forming and Relative Dielectric Constant of Formed Film

[0094]FIG. 6 is a view showing relations, each between low-frequency electric power applied to the lower electrode 3 for forming direct current bias voltage to a substrate subject to film forming and a relative dielectric constant of a film formed on a silicon substrate. The axis of ordinates thereof shows the relative dielectric constant of a formed film scaled by linear graduations. The axis of abscissas shows the low-frequency electric power (W) scaled by linear graduations.

[0095] Insulating films for examination were formed on silicon substrates in accordance with the above-described conditions for film forming under three conditions of the gas pressure of the film-forming gas by 0.9, 1.2 and 1.5 Torr, respectively, and under six conditions of the low-frequency electric power of 0, 10, 20, 50, 75 and 100 W, respectively. The relative dielectric constants were measured by the C-V method, in which a signal of a frequency of 1 MHz is superposed on a direct current bias.

[0096] Note that, in the case of the gas pressure of 1.5 Torr in the drawing, the numerals near the examination points represent the film hardness.

[0097] According to FIG. 6, in the case of the gas pressure of 0.9 Torr, the relative dielectric constant sharply increases in a range of the low-frequency electric power from 0 to 20 W, which was observed as ranging from about 2.9 to 4.3. The relative dielectric constant then gently decreases as the low-frequency electric power further increases beyond 20 W. In the case of the gas pressure of 1.2 Torr, the relative dielectric constant sharply increases in a range of the low-frequency electric power from 0 to 20 W, which was observed as ranging from about 2.7 to 3.9. The relative dielectric constant gently increases beyond 20 W to be about 4.8 at 100 W. Also, in the case of the gas pressure of 1.5 Torr, similarly to the case of the gas pressure of 1.2 Torr, the relative dielectric constant sharply increases in a range of the low-frequency electric power from 0 to 20 W, which was observed as ranging from about 2.7 to 3.6. The relative dielectric constant gently increases beyond 20 W to be about 4.1 at 100 W.

[0098] As described above, according to the first embodiment, it turned out that, concerning the gas pressure of the film-forming gas, the exfoliation intensity is large when the pressure is low, however, the relative dielectric constant becomes high. In particular, the exfoliation intensity is large at lower than 1 Torr, and the relative dielectric constant is low at 1 Torr or higher. And concerning the low-frequency electric power, the exfoliation intensity becomes high and the relative dielectric constant becomes low when the electric power is low.

[0099] Therefore, in the case of forming an insulating film having a low dielectric constant as an interlayer insulating film between wiring primarily made of a copper film, it is preferable to lower gas pressure such as below 1 Torr for example, and to lower low-frequency electric power in an initial stage of film-forming, thus enhancing exfoliation intensity at a little sacrifice of a relative dielectric constant, then for the remainder, to perform film forming with gas pressure of 1 Torr or higher for example, thus lowering the relative dielectric constant of the entire film.

[0100] Moreover, in the case of forming an insulating film having a low dielectric constant as a barrier insulating film contacting with wiring primarily made of a copper film, the gas pressure will be adjusted for a low-pressure insulating film and a high-pressure insulating film as similarly to the case of forming the interlayer insulating film, while a frequency of the electric power for plasma excitation will not be adjusted but maintained to a low frequency for both the low-pressure insulating film as well as the high-pressure insulating film. That is, it is preferable to lower the gas pressure such as below 1 Torr for example, and to lower the low-frequency electric power in an initial stage of film-forming, thus enhancing exfoliation intensity at a little sacrifice of a relative dielectric constant, then for the remainder, to perform film forming with gas pressure of 1 Torr or higher for example, thus lowering the relative dielectric constant of the entire film.

[0101] It should be noted that, although gas pressure below 1 Torr is preferable at the initial stage of film forming, the gas pressure below 0.1 Torr brings a slow film-forming rate hence it is not practical. Moreover, whereas the gas pressure of 1 Torr or higher is preferable for forming the rest of the film, the gas pressure within the maximum of 10 Torr is practical in light of electrical discharge.

Second Embodiment

[0102] Next, a semiconductor device and a method of manufacturing the same according to a second embodiment of the present invention will be described with reference to the FIG. 8A and FIG. 8B.

[0103]FIG. 8A is a cross-sectional view showing a semiconductor device produced by the method of manufacturing a semiconductor device according to the second embodiment of the present invention. FIG. 8B is a cross-sectional view of FIG. 8A taken along a line I-I. A film-forming gas composed of HMDSO+N₂O+He is used in order to form an interlayer insulating film 34 between wiring-embedded films, the interlayer insulating film being sandwiched a lower wiring-embedded insulating film 32 where lower wiring 33 is embedded and an upper wiring-embedded insulating film 35 where upper wiring 37 is embedded.

[0104] Firstly, as shown in FIG. 8A, the wiring-embedded insulating film 32 is formed on a base substrate 31, the wiring-embedded insulating film being composed of either a SiO₂ film or a SiOCH film in a film thickness of about 1 μm. It should be noted that the SiOCH film is an insulating film that contains Si, O, C and H.

[0105] Subsequently, a wiring groove is formed by etching the wiring-embedded insulating film 32, thereafter a TaN film 33 a is formed inside the wiring groove as a anti-diffusion film for copper. Next, an unillustrated copper seed layer is formed on a surface of the TaN film 33 a by a sputtering method, then a copper film is embedded by a plating method. The copper film and the TaN film 33 a projected from the wiring groove are then subjected to polishing by a chemical mechanical polishing (CMP) method, thus the surface of the lower wiring is planarized. The lower wiring composed of the wiring 33 b primarily made of the copper film and the TaN film 33 a is thereby formed.

[0106] Next, the interlayer insulating film 34 between wiring-embedded films, composed of a PE-CVD SiOCH film in a film thickness of several tens of nanometers, is formed by a plasma enhanced CVD method using HMDSO+N₂O+He. Detail description thereof will be made hereunder.

[0107] Specifically, in order to form the interlayer insulating film 34 between wiring-embedded films, a substrate 21 is introduced to a chamber 1 of a film-forming apparatus 101, and is held on a substrate holder 3. Subsequently, the substrate 21 is heated and maintained at a temperature of 375° C. HMDSO at a flow rate of 50 sccm, N₂O gas at a flow rate of 200 sccm, and He gas at a flow rate of 400 sccm are introduced to the chamber 1 of the plasma film-forming apparatus 101 as shown in FIG. 1, and maintained at pressure of 0.7 Torr. Thereafter, low-frequency electric power of a frequency of 380 kHz in a range from 100 to 150 W is applied to a lower electrode 3, and high-frequency electric power of a frequency of 13.56 MHz at 250 W (equivalent to 0.3 W/cm²) is applied to an upper electrode 2.

[0108] HMDSO, N₂O and He are thereby converted into plasma. This state is maintained for 40 seconds, thus a low-pressure insulating film 34 a composed of a PE-CVD SiOC film in a film thickness of about 100 nm is formed. Note that the SiOC film is an insulating film that contains Si, O and C within the film.

[0109] Successively, film forming is performed with the same combination of the reactive gases, the same flow rates thereof, under the gas pressure adjusted to 1.5 Torr, and under the same condition for the plasma excitation. A high-pressure insulating film 34 b composed of a PE-CVD SiOCHfilm in a film thickness of about 500 nm is thereby formed.

[0110] As described above, the interlayer insulating film 34 between wiring-embedded films, composed of the low-pressure insulating film 34 a and the high-pressure insulating film 34 b, is thereby formed.

[0111] Next, the wiring-embedded insulating film 35 composed of either a SiO₂ film or a SiOCH film in a film thickness of about 1 μm is formed on the interlayer insulating film 34 between wiring-embedded layers, by the same method used for forming either the SiO₂ film or the SiOCH film 32.

[0112] Next, a connecting conductor 36 and upper wiring 37 primarily made of a copper film are formed by the well-known dual-damascene method. In the drawing, it should be noted that the reference numerals 36 a and 37 a denote a TaN film and reference numerals 36 b and 37 b denote a copper film.

[0113] Next, a barrier insulating film 38 is formed on an entire top surface. The semiconductor device is thereby formed.

[0114] As describe above, according to this second embodiment, in a method of manufacturing a semiconductor device in which the interlayer insulating film 34 for wiring-embedded films is sandwiched between the lower wiring-embedded insulating film 32 where the lower wiring 33 is embedded therein and the upper wiring-embedded insulating film 35 where the upper wiring 37 is embedded therein, initial film-forming is performed under a gas pressure of a film-forming gas below 1 Torr, and film-forming for the remainder is performed under the gas pressure of 1 Torr or higher by means of the plasma enhanced CVD method in order to form the interlayer insulating film 34 for wiring-embedded films.

[0115] The interlayer insulating film 34 for wiring-embedded films with high adhesion to the copper film 33 b and with a low relative dielectric constant of 3 or less as a whole can be thereby formed.

[0116] The present invention has been described in detail with the second embodiment. However, it should be understood that the scope of the invention is not limited to the example particularly shown in the above-described embodiment, and that various modifications of the above embodiment not departing from the gist of the invention shall be also deemed within the scope of the invention.

[0117] Instead of HMDSO as used in the second embodiment, another alkyl compound having a siloxane bond as described in the first embodiment, or methylsilane (SiH_(n)(CH₃)_(4-n): n=0, 1, 2, 3) may be used. As for variations of the methylsilane, description will be omitted here as they have been indicated in the first embodiment.

[0118] Moreover, as for the film-forming gas, one containing any one of acetylene (C₂H₂), methylcyclohexane (CH₃C₆H₁₁) and cyclohexane (C₆H₁₂) may be used. A porous property of the film will be enhanced, and thus the dielectric constant will be further decreased.

[0119] Moreover, the film-forming gas may be one that contains benzene (C₆H₆).

[0120] Furthermore, the film-forming gas may be one that contains either methyl alcohol (CH₃OH) or ethyl alcohol (C₂H₅OH).

[0121] Furthermore, any one of argon (Ar) and nitrogen (N₂) may be added to the film-forming gas instead of helium (He).

[0122] Still further, the barrier insulating film 38 may be formed by the same method of film forming as that of forming a barrier insulating film 39 a described hereunder in a third embodiment.

Third Embodiment

[0123]FIG. 9A is a cross-sectional view showing a method of manufacturing a semiconductor device according to a third embodiment of the present invention. FIG. 9B is a cross-sectional view of FIG. 9A taken along a line II-II.

[0124] A deference from the FIG. 8A and FIG. 8B is that, of an interlayer insulating film 39 that includes barrier insulating films 39 a and 39 c, the manufacturing method of the invention is applied particularly to the barrier insulating film 39 a that contacts with the wiring primarily made of a copper film.

[0125] The method of manufacturing a semiconductor device according to the third embodiment will be described in the following. Regarding FIG. 9A and FIG. 9B, it should be noted that the elements indicated with the same reference numerals as those indicated in FIG. 8A and FIG. 8B. represent the same, accordingly, description in this regard will be omitted.

[0126] Firstly, by the method similar to the second embodiment, a wiring-embedded insulating film 32 is formed on a base substrate 31, the wiring-embedded insulating film being composed of either a SiO₂ film or a SiOCH film in a film thickness of about 1 μm. And, lower wiring composed of wiring 33 b primarily made of a copper film and a TaN film 33 a is formed in a wiring groove of the wiring-embedded insulating film 32.

[0127] Next, of the interlayer insulating film 39 between wiring-embedded layers, the barrier insulating film 39 a that contacts with the copper film is formed by a plasma enhanced CVD method using a film-forming gas composed of HMDSO+N₂O+NH₃. Detail description thereof will be made hereunder.

[0128] Specifically, in order to form the barrier insulating film 39 a, a substrate 21 is introduced to a chamber 1 of a film-forming apparatus 101, and is held on a substrate holder 3. Subsequently, the substrate 21 is heated and maintained at a temperature of 375° C. HMDSO at a flow rate of approximately 50 sccm, N₂O at a flow rate of approximately 200 sccm, and NH₃ gas at a flow rate of approximately 50 sccm are introduced to the chamber 1 of the plasma film-forming apparatus 101 as shown in FIG. 1, and maintained at pressure of 0.7 Torr. Note that He gas may be also added to the above-described film-forming gas. In this case, a flow rate thereof is satisfactorily set to 400 sccm.

[0129] Thereafter, low-frequency electric power of a frequency of 380 kHz in about 150 W is applied to a lower electrode 3. High-frequency electric power is not applied to an upper electrode 2.

[0130] HMDSO, N₂O and NH₃ are thereby converted into plasma. This state is maintained for 5 seconds, thus a low-pressure insulating film 39 a a composed of a PE-CVD SiO₂ film in a film thickness of 10 nm is formed.

[0131] Successively, film forming is performed with the same combination of the reactive gases, the same flow rates thereof, under the gas pressure adjusted to 1.5 Torr, and under the same condition for the plasma excitation. A high-pressure insulating film 39 ab composed of a PE-CVD SiOCN film in a film thickness of about 90 nm is thereby formed.

[0132] As described above, the barrier insulating film 39 a composed of the low-pressure film 39 aa and the high-pressure film 39 ab is formed.

[0133] Next, on the barrier insulating film 39 a, a main insulating film 39 b having a low dielectric constant and a barrier insulating film 39 c are serially formed by a generally known method of forming an insulating film having a low dielectric constant. The interlayer insulating film 39 between wiring-embedded layers is thereby formed.

[0134] Next, on the interlayer insulating film 39 between wiring-embedded layers, a wiring-embedded insulating film 35, a connecting conductor 36, upper wiring 37 and a barrier insulating film 38 are formed in this order from the bottom.

[0135] As described above, according to this embodiment, when the interlayer insulating film 39 including the barrier insulating films 39 a and 39 c is formed on wiring primarily made of a copper film, initial film-forming is performed so as to form a low-pressure insulating film 39 aa and the remainder is formed as a high-pressure insulating film 39 ab in order to form the barrier insulating film 39 a. And in the courses of forming both the low-pressure insulating film 39 aa and the high-pressure insulating film 39 ab, the film-forming gas is converted into plasma by use of the low-frequency electric power.

[0136] Film forming with low-frequency electric power originally imparts a strong adhesion force. However, by forming a film while using a film-forming gas of a low gas pressure, adhesion strength can be further improved.

[0137] The present invention has been described in detail with the third embodiment. However, it should be understood that the scope of the invention is not limited to the example particularly shown in the above-described embodiment, and that various modifications of the above embodiment not departing from the gist of the invention shall be also deemed within the scope of the invention.

[0138] Instead of HMDSO as used in the third embodiment, another alkyl compound having a siloxane bond as described in the first embodiment, or methylsilane (SiHn(CH₃)_(4-n): n=0, 1, 2, 3) may be used. As for variations of the methylsilane, description will be omitted here as they have been indicated in the first embodiment.

[0139] Moreover, the film-forming gas may contain a nitrogen-containing gas of any one of ammonia (NH₃) and nitrogen (N₂).

[0140] Furthermore, the film-forming gas may contain any one of helium (He), argon (Ar) and nitrogen (N₂). So-called “clouded” in a formed film may be thereby prevented.

[0141] Still further, the barrier insulating film 39 b out of the interlayer insulating film 39 may be formed by the same method of forming the insulating film 34 b as described in the second embodiment. Moreover, the barrier insulating film 39 c out of the interlayer insulating film 39 may be formed by the same method of forming the insulating film 39 a, provided that a side contacting with the upper wiring 37 should be formed as a low-pressure insulating film. Furthermore, the barrier insulating film 38 may be formed by the same method of forming the barrier insulating film 39 a.

Fourth Embodiment

[0142] The above-described embodiments describe with respect to forming a barrier insulating film on the main insulating film having a low dielectric constant. However, this invention is advantageous for an object of just forming the main insulating film having a low dielectric constant using same film-forming gas. In this case, the gas pressure does not have to be changed during the film forming. By use of a film-forming gas containing: an alkyl compound having a siloxane bond; any one of acetylene (C₂H₂), methylcyclohexane (CH₃C₆H₁₁) and cyclohexane (C₆H₁₂); and an oxygen-containing gas, or a film-forming gas containing; an alkyl compound having a siloxane bond; benzene (C₆H₆); an oxygen-containing gas; and an inert gas, a desired main insulating film can be formed while maintaining an equal gas pressure.

[0143] Now, a method of manufacturing a semiconductor device according to a fourth embodiment will be described with reference to FIG. 9A and FIG. 9B.

[0144] A deference from the third embodiment is that, of an interlayer insulating film 39 that includes the upper and lower barrier insulating films 39 a and 39 c and the main insulating film 39 b having a low dielectric constant, the manufacturing method of the invention is applied particularly to the main barrier insulating film 39 b having a low dielectric constant and sandwiched by the barrier insulating films 39 a and 39 c.

[0145] The method of manufacturing a semiconductor device according to the fourth embodiment will be described hereunder. Film-forming conditions for the main insulating film 39 b are as follows:

Film-forming Gas

[0146] HMDSO flow rate: 50 sccm N₂O flow rate: 200 sccm CH₃C₆H₁₁ flow rate: 50 sccm gas pressure: 0.9 Torr

Conditions for Plasma Excitation

[0147] Lower electrode (first electrode)

[0148] low-frequency electric power (frequency 380 kHz) (parameter): 0 W

[0149] Upper electrode (second electrode)

[0150] high-frequency electric power (frequency 13.56 MHz) (parameter): 250 W

[0151] Condition for substrate heating: 375° C.

[0152] Firstly, by the method similar to the second embodiment, a wiring-embedded insulating film 32 is formed on a base substrate 31, the wiring-embedded insulating film being composed of a PE-CVD SiO₂ film in a film thickness of about 1 μm. And, lower wiring composed of wiring 33 b primarily made of a copper film and a TaN film 33 a is formed in a wiring groove of the wiring-embedded insulating film 32.

[0153] Next, of the interlayer insulating film 39 between wiring-embedded layers, the barrier insulating film 39 a that contacts with the copper film is formed by a plasma enhanced CVD method using a film-forming gas composed of HMDSO+N₂O+NH₃, similarly to the third embodiment. The barrier insulating film 39 a includes a low-pressure insulating film 39 aa and a high-pressure insulating film 39 ab.

[0154] Next, on the barrier insulating film 39 a, a main insulating film 39 b having a low dielectric constant and a barrier insulating film 39 c are serially formed by the plasma enhanced CVD method using the film-forming gas of the above-described film-forming conditions. The interlayer insulating film 39 between wiring-embedded layers is thereby formed.

[0155] In order to form the main insulating film 39 b having a low dielectric constant, firstly, a substrate 21 is introduced to a chamber 1 of a film-forming apparatus 101, and is held on a substrate holder 3. Subsequently, the substrate 21 is heated and maintained at a temperature of 375° C. HMDSO at a flow rate of 50 sccm, N₂O gas at a flow rate of 200 sccm, and CH₃C₆H₁₁ at a flow rate of 50 sccm are introduced to the chamber 1 of the plasma film-forming apparatus 101 as shown in FIG. 1, and maintained at pressure of 0.9 Torr. Next, high-frequency electric power of a frequency of 13.56 MHz in about 250 W (equivalent to 0.3 W/cm²) is applied to an upper electrode 2. In this event, low-frequency electric power is not applied to a lower electrode 3.

[0156] HMDSO, N₂O and CH₃C₆H₁₁ are thereby converted into plasma. This state is maintained for 40 seconds, thus the main insulating film 39 b composed of a PE-CVD SiO₂ film in a film thickness of about 500 nm is formed.

[0157] Next, on the interlayer insulating film 39 between wiring-embedded layers, a wiring-embedded insulating film 35, a connecting conductor 36, upper wiring 37 and a barrier insulating film 38 are serially formed similarly to the second embodiment.

[0158] The present invention has been described in detail with the fourth embodiment. However, it should be understood that the scope of the invention is not limited to the example particularly shown in the above-described embodiments, and that various modifications of the above embodiments not departing from the gist of the invention shall be also deemed within the scope of the invention.

[0159] Instead of HMDSO as used in the fourth embodiment, another alkyl compound having a siloxane bond as described in the first embodiment, or methylsilane (SiH_(n)(CH₃)_(4-n): n=0, 1, 2, 3) may be used. As for variations of the methylsilane, description will be omitted here as they have been indicated in the first embodiment.

[0160] Moreover, the film-forming gas may contain any one of helium (He), argon (Ar) and nitrogen (N₂). In this case, benzene (C₆H₆) may be used instead of any one of acetylene (C₂H₂), methylcyclohexane (CH₃C₆H₁₁) and cyclohexane (C₆H₁₂).

[0161] As described above, according to the present invention, either an interlayer insulating film being sandwiched between a plurality of wiring primarily made of copper films, or a barrier insulating film that contact with wiring primarily made of a copper film is formed by a plasma enhanced CVD method using at least: an alkyl compound having a siloxane bond or methylsilane (SiH_(n)(CH₃)_(4-n): n=0, 1, 2, 3); and an oxygen-containing gas of any one of N₂O, H₂O and CO₂, wherein film forming is performed under a low gas pressure (below 1 Torr) at an initial stage of film forming, and under a high gas pressure (at 1 Torr or higher) for the remainder of the film forming.

[0162] By lowering the gas pressure, an insulating film favorable in adhesion to wiring primarily made of a copper film can be formed. And, by raising the gas pressure, an insulating film of a low dielectric constant can be formed.

[0163] Therefore, formation of an interlayer insulating film favorable in adhesion to wiring primarily made of a copper film, as well as with a low dielectric constant becomes feasible.

[0164] Moreover, by forming a barrier insulating film by applying low-frequency electric power and performing the above-described two-step adjustment, formation of the barrier insulating film more favorable in adhesion to wiring primarily made of a copper film becomes feasible.

[0165] Furthermore, within an object of just forming a main insulating film having a low dielectric constant, the gas pressure does not have to be changed during the film forming. By use of a film-forming gas containing: an alkyl compound having a siloxane bond; any one of acetylene (C₂H₂), methylcyclohexane (CH₃C₆H₁₁) and cyclohexane (C₆H₁₂); and an oxygen-containing gas or a film-forming gas containing, or by use of a film-forming gas containing: an alkyl compound having a siloxane bond; benzene (C₆H₆); an oxygen-containing gas; and an inert gas, a desired main insulating film can be formed while maintaining an equal gas pressure. 

What is claimed is:
 1. A method of manufacturing a semiconductor device in which an insulating film having a low dielectric constant is formed on a substrate by allowing a film-forming gas to be converted into a plasma state and to react, said method comprising the steps of: forming a low-pressure insulating film which constitutes said insulating film on said substrate, by allowing said film-forming gas at a first gas pressure to be converted into a plasma state and to react; and forming a high-pressure insulating film which constitutes said insulating film on said low-pressure insulating film, by allowing said film-forming gas at a second gas pressure higher than the first gas pressure to be converted into a plasma state and to react.
 2. The method of manufacturing a semiconductor device according to claim 1, wherein said first gas pressure is 0.1 Torr or higher, but below 1 Torr, and said second gas pressure is in the range of 1 Torr to 10 Torr.
 3. The method of manufacturing a semiconductor device according to claim 1, wherein electrodes of parallel plate type composed of a first electrode holding said substrate and a second electrode opposing to said first electrode are used as means for forming said plasma, a low-frequency electric power of a frequency of 100 kHz or higher but below 1 MHz is applied to said first electrode in the step of forming said low-pressure insulating film, and a high-frequency electric power of 1 MHz or higher is applied to said second electrode in the step of forming said high-pressure insulating film.
 4. The method of manufacturing a semiconductor device according to claim 3, wherein said low-frequency electric power is applied to said first electrode in addition to application of said high-frequency electric power to said second electrode in the step of forming said high-pressure insulating film.
 5. The method of manufacturing a semiconductor device according to claim 3, wherein said high-frequency electric power is applied to said second electrode simultaneously in addition to application of said low-frequency electric power to said first electrode in the step of forming said low-pressure insulating film.
 6. The method of manufacturing a semiconductor device according to claim 5, wherein said low-frequency electric power is applied to said first electrode in addition to application of said high-frequency electric power to said second electrode in the step of forming said high-pressure insulating film.
 7. The method of manufacturing a semiconductor device according to claim 1, wherein electrodes of parallel plate type composed of a first electrode holding said substrate and a second electrode opposing to said first electrode are used as means for forming said plasma, a low-frequency electric power of a frequency of 100 kHz or higher but below 1 MHz is applied to said first electrode in said step of forming said low-pressure insulating film, and said low-frequency electric power is applied to said first electrode in said step of forming said high-pressure insulating film.
 8. The method of manufacturing a semiconductor device according to claim 1, wherein said film-forming gas is composed of: an alkyl compound having a siloxane bond; and an oxygen-containing gas of any one of N₂O, H₂O and CO₂.
 9. The method of manufacturing a semiconductor device according to claim 8, wherein said alkyl compound having a siloxane bond is any one of hexamethyldisiloxane (HMDSO: (CH₃)₃Si—O—Si(CH₃)₃), octamethylcyclotetrasiloxane (OMCTS: ((CH₃)₂)₄Si₄O₄

tetramethylcyclotetrasiloxane (TMCTS: (CH₃H)₄ Si₄O₄


10. The method of manufacturing a semiconductor device according to claim 1, wherein said film-forming gas contains methylsilane (SiHn(CH3)4-n: n=0, 1, 2, 3).
 11. The method of manufacturing a semiconductor device according to claim 10, wherein said methylsilane (SiH_(n)(CH₃)_(4-n): n=0, 1, 2, 3) is any one of monomethylsilane (SiH₃ (CH₃)) dimethylsilane (SiH₂ (CH₃)₂), trimethylsilane (SiH(CH₃)₃) and tetramethylsilane (Si(CH₃)₄).
 12. The method of manufacturing a semiconductor device according to claim 1, wherein said film-forming gas contains any one of methylcyclohexane (CH₃C₆ H₁₁) and cyclohexane (C ₆H₁₂).
 13. The method of manufacturing a semiconductor device according to claim 1, wherein said film-forming gas contains benzene (C ₆H6).
 14. The method of manufacturing a semiconductor device according to claim 1, wherein said film-forming gas contains any one of methyl alcohol (CH₃OH) and ethyl alcohol (C₂H₅OH).
 15. The method of manufacturing a semiconductor device according to claim 1, wherein said film-forming gas contains any one of ammonia (N H₃) and nitrogen (N₂).
 16. The method of manufacturing a semiconductor device according to claim 1, wherein said film-forming gas contains any one of helium (He), argon (Ar) and nitrogen (N₂).
 17. A semiconductor device comprising: an insulating film of a low dielectric constant being formed of a lower-pressure insulating film on a wiring primarily made of a copper film to contact with the wiring primarily made of a copper film and a high-pressure insulating film on the lower-pressure insulating film, wherein said lower-pressure insulating film is formed by allowing said film-forming gas at a first gas pressure to be converted into a plasma state and to react, and the high-pressure insulating film is formed by allowing said film-forming gas at a second gas pressure higher than the first gas pressure to be converted into a plasma state and to react.
 18. The semiconductor device according to claim 17, wherein said insulating film formed on the wiring primarily made of a copper film constitutes an interlayer insulating film sandwiched by a plurality of wiring primarily made of copper films.
 19. A semiconductor device comprising: a barrier insulating film being formed of a lower-pressure insulating film on a wiring primarily made of a copper film to contact with the wiring primarily made of a copper film and a high-pressure insulating film on the lower-pressure insulating film; and an insulating film on said barrier insulating film, wherein using electrodes of parallel plate type composed of a first electrode holding said substrate and a second electrode opposing to said first electrode as means for forming a plasma, said low-pressure insulating film is formed by applying low-frequency electric power of a frequency of 100 kHz or higher but below 1 MHz to said first electrode, and said high-pressure insulating film is formed by applying said low-frequency electric power to said first electrode.
 20. The semiconductor device according to claim 19, wherein said barrier insulating film and said insulating film on said barrier film collectively constitutes an interlayer insulating film sandwiched by a plurality of wirings primarily made of copper films.
 21. A method of manufacturing a semiconductor device in which an insulating film of a low dielectric constant is formed on a substrate by allowing a film-forming gas to be converted into a plasma state and to react, wherein said film-forming gas is composed of an alkyl compound having a siloxane bond, a hydrocarbon (C_(x)H_(y)) and an oxygen-containing gas.
 22. The method of manufacturing a semiconductor device according to claim 21, wherein said alkyl compound having a siloxane bond is any one of hexamethyldisiloxane (HMDSO: (CH₃)₃Si—O—Si(CH₃)₃), octamethylcyclotetrasiloxane (OMCTS: ((CH₃)₃)₄Si₄O₄

tetramethylcyclotetrasiloxane (TMCTS: (CH₃H)₄Si₄O₄


23. The method of manufacturing a semiconductor device according to claim 21, wherein said hydrocarbon (C_(x)H_(y)) is any one of acetylene (C₂H₂), methylcyclohexane (CH₃H₆H₁₁), cyclohexane (C₆H₁₂) and benzene (C₆H₆).
 24. The method of manufacturing a semiconductor device according to claim 21, wherein said film-forming gas contains methylsilane (SiH_(n)(CH₃)_(4-n): n=0, 1, 2, 3) instead of said alkyl compound having a siloxane bond.
 25. The method of manufacturing a semiconductor device according to claim 24, wherein said methylsilane (SiH_(n)(CH₃)_(4-n): n=0, 1, 2, 3) is any one of monomethylsilane (SiH₃(CH₃)), dimethylsilane (SiH₂(CH₃)₂), trimethylsilane (SiH(CH₃)₃) and tetramethylsilane (Si(CH₃)₄).
 26. The method of manufacturing a semiconductor device according to claim 21, wherein said film-forming gas contains any one of helium (He), argon (Ar) and nitrogen (N₂).
 27. A semiconductor device comprising: an insulating film of a low dielectric constant formed on a wiring primarily made of a copper film, wherein said insulating film is formed by allowing a film-forming gas composed of: an alkyl compound having a siloxane bond, a hydrocarbon (C_(x)H_(y)), and an oxygen-containing gas to be converted into a plasma state and to react.
 28. The semiconductor device according to claim 27, wherein said insulating film formed on the wiring primarily made of a copper film constitutes an interlayer insulating film sandwiched by a plurality of wiring primarily made of copper films.
 29. A semiconductor device comprising: a barrier insulating film formed on said a wiring primarily made of a copper film to contact with the wiring primarily made of a copper film; and an insulating film of a low dielectric constant formed on said barrier insulating film, wherein said insulating film is formed by allowing a film-forming gas composed of: an alkyl compound having a siloxane bond, a hydrocarbon (C_(x)H_(y)), and an oxygen-containing gas to be converted into a plasma state and to react.
 30. The semiconductor device according to claim 29, wherein said barrier insulating film and said insulating film constitute an interlayer insulating film sandwiched by a plurality of wirings primarily made of copper films. 